The present invention relates to material handling apparatus for altering the orientation of an article between different stages of a manufacturing process. More specifically, it relates to an apparatus and method for inverting a plurality of delicate, non-planar work pieces (e.g., contact lenses) between separate manufacturing processing steps which require, for example, sequential processing treatments to the opposite concave-convex surfaces of the lenses.
Small, delicate work pieces such as contact lenses pose a significant handling problem as to the method(s) by which they are moved through multiple stages of a manufacturing process. Since scratched, cracked or broken lenses must be rejected and scrapped, it is highly desirable to develop material handling methods which make minimum direct contact with the lenses so as to reduce the chance of destructive damage thereto. The necessity for total inversion of a lens from one manufacturing processing stage to another may indeed present the greatest material handling challenge for this type of work piece. Total inversion of a contact lens is required, for example, when effecting plasma treatments to the opposite convex and concave surfaces of silicone hydrogel lenses. Heretofore, inversion of contact lenses between plasma treatments to the opposite surfaces of a lens has been effected manually with a pair of tweezers, a laborious process that is expensive, time consuming, and may contribute to worker repetitive motion injuries.
A known material handling apparatus for inverting an ophthalmic lens between manufacturing processing steps is seen in U.S. Pat. No. 4,006,563 issued to Essilor International on Feb. 8, 1977. In the '563 machine, non-planar, ophthalmic mouldings are inverted, one at a time, as they are released from a suction cup mechanism 75 adjacent a tipping rod 83 which extends transversely above a moving conveyor belt. As the moulding is released, the leading edge thereof strikes the tipping rod while the trailing edge falls onto the conveyor belt, with the tipping rod and moving conveyor belt acting together to flip the moulding over onto the belt (ending convex side up). The lens travels to the opposite end of the conveyor belt where it is picked up by a second suction cup mechanism and deposited at a second battery of work stations.
While the '563 machine appears effective at inverting an ophthalmic lens between two batteries of work stations, it would not be an acceptable means for inverting a finished contact lens since the striking of the lens edge against a tipping rod would likely cause destructive damage to the lens resulting in unacceptably high numbers of reject lenses. Furthermore, it is apparent the '563 mechanism can invert only one moulding at a time which makes it inefficient for use in high volume production environments such as the contact lens manufacturing business.
It is also known to use a controlled, compressed air stream in article orienting apparatus. For example, as seen in U.S. Pat. No. 3,734,268 which issued to Burger et al on May 22, 1973, an air stream is used to flip any lids which are in a "down skirt" position traveling along a conveyor belt 18 to an "upskirt" position. (The term "down skin"means the hollow of the lid formed by the circular flat portion and circumscribing vertical wall ("skin") is facing downwardly on the belt. "Up skirt"means the hollow is facing upwardly on the belt.) The air stream 48 is directed upwardly through an opening 38 formed in a horizontal shelf 36 over which belt 18 extends. Laterally and longitudinally spaced curved walls 34 and 52 located on opposite sides of belt 18 direct the lids, one at a time, into a position where a side edge of each passing lid (facing wall 52) slightly overhangs the corresponding side edge of the belt. With the opening 38 in the underlying shelf 36 being located outwardly adjacent to this edge of the belt, the air stream is directed to impinge against the downwardly facing surface of the overhanging portion of the lid. Thus, lids in the "down skirt" position will be flipped over in a lateral direction to an "up skin" position by the air stream due to the forces acting against the hollow of the lid. Apparently, lids already in the "up skirt"position are not affected by the air stream.
While the '268 device appears suitable for inverting durable plastic lids as they travel down a conveyor belt, it would not be an acceptable method for inverting very delicate articles such as contact lenses since a lens edge would likely be damaged as it is forced into the correct position by the wall members 34 and 52. Additionally, the '268 mechanism does not provide for the orientation of more than one article at a time, a desirable feature in high volume production environments such as the contact lens manufacturing business.
There thus exists a need for an inexpensive, reliable and safe apparatus and method for inverting a plurality of contact lenses as they are transferred from one manufacturing process step to another, while also maintaining an acceptable scrap ratio caused by the material handling method.